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Conference on Medical Imaging - Image-Guided Procedures, Robotic Interventions, and Modeling

作者： Ma, Burton Banihaveb, Niloofar Choi, Joy Chen, Elvis C. S. Simpson, Amber L. York Univ Dept Elect Engn & Comp Sci Toronto ON Canada Western Univ Robarts Res Inst London ON Canada Mem Sloan Kettering Canc Ctr Hepatopancreatobiliary Serv New York NY USA

ISBN: (数字)9781510607163

ISBN: (纸本)9781510607156;9781510607163

Calibrating a pointing stylus tracked via a dynamic reference frame (DRF) is often performed by pivoting the stylus on its tip in a divot located at a fixed position in the tracking system coordinate frame. The calibration problem is solved by estimating the location of the fixed divot position. Recent work (Yaniv,, Which pivot calibration?, Proceedings of SPIE Vol. 941527, 2015) provided evidence that solving the calibration problem using the measured poses of the stylus during pivoting is superior to fitting the measured position of the DRF during pivoting to a sphere. We constructed apparatus to acquire very high quality pivoting measurements over a much wider range of pivoting angles than could be obtained by pivoting in a divot. We tested pose-based calibration and sphere fitting and found that sphere fitting was as precise as (if not better than) pose-based calibration when using high-quality pivoting data. We performed a simple simulation where the stylus tip location deviated by a small amount during pivoting and found that the precision of sphere fitting degraded much more than pose-based calibration which suggests that pose-based calibration should be favored over sphere fitting when non-perfect pivoting is not possible.

关键词： calibration localization and tracking technologies validation and evaluation

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Which Pivot Calibration?

Which Pivot Calibration?

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Conference on Medical Imaging - Image-Guided Procedures, Robotic Interventions, and Modeling

作者： Yaniv, Ziv NIH Off High Performance Comp & Commun Natl Lib Med Bethesda MD 20894 USA

ISBN: (纸本)9781628415056

Estimating the location of a tracked tool's tip relative to its Dynamic Reference Frame (DRF) and localizing a specific point in a tracking system's coordinate frame are fundamental tasks in image-guided procedures. The most common approach to estimating these values is by pivoting a tool around a fixed point. The transformations from the tracking system's frame to the tool's DRF are the input. The output is the translation from the DRF to the tool's tip and the translation from the tracker's frame to the pivoting point. While the input and output are unique, there are multiple mathematical formulations for performing this estimation task. The question is, are these formulations equivalent in terms of precision and accuracy? In this work we empirically evaluate three common formulations, a geometry based sphere fitting formulation and two algebraic formulations. In addition we evaluate robust variants of these formulations using the RANSAC framework. Our evaluation shows that the algebraic formulations yield estimates that are more precise and accurate than the sphere fitting formulation. Using the Vicra optical tracking system from Northern Digital Inc., we observed that the algebraic approaches have a mean(std) precision of 0.25(0.11)mm localizing the pivoting point relative to the tracked DRF, and yield a fiducial registration error with a mean(std) 0.15(0.08)mm when registering a precisely constructed divot phantom to the localized points in the tracking system's frame. The sphere fitting formulation yielded less precise and accurate results with a mean(std) of 0.35(0.21)mm for precision and 0.25(0.14)mm for accuracy. The robust versions of these formulations yield similar results even when the data is contaminated with 30% outliers.

关键词： calibration localization and tracking technologies validation and evaluation

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Hybrid electromagnetic and image-based tracking of endoscopes with guaranteed smooth output

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INTERNATIONAL JOURNAL OF COMPUTER ASSISTED RADIOLOGY AND SURGERY 2013年第6期8卷 955-965页

作者： Reichl, Tobias Luo, Xiongbiao Menzel, Manuela Hautmann, Hubert Mori, Kensaku Navab, Nassir TUM Munich Germany Nagoya Univ Nagoya Aichi 4648601 Japan TUM Klinikum Rechts Isar Med Klin 1 Munich Germany

Flexible fiber-optic bronchoscopy is a widespread medical procedure for the diagnosis and treatment of lung diseases. Navigation systems are needed to track the flexible endoscope within the bronchial tree. Electromagnetic (EM) tracking is currently the only technology used clinically for this purpose. The registration between EM tracking and patient anatomy may become inaccurate due to breathing motion, so the addition of image-based tracking has been proposed as a hybrid EM-image-based system. When EM tracking is used as an initialization for image registration, small changes in the initialization may lead to different local minima and noise is amplified by hybrid tracking. The tracking output is modeled as continuous and uses splines for interpolation, thus smoothness is greatly improved. The bronchoscope pose relative to computed tomography data is interpolated using Catmull-Rom splines for position and spherical linear interpolation (SLERP) for orientation. The hybrid method was evaluated using ground truth poses manually selected by experts, where mean inter-expert agreement was determined as 1.26 mm. Using four dynamic phantom data sets, the accuracy was 4.91 mm, which is equivalent to previous methods. Compared to state-of-art methods, inter-frame smoothness was improved from 2.77-3.72 to 1.24 mm. Hybrid image and electromagnetic endoscope guidance provides a more realistic and physically plausible solution with significantly less jitter. This quantitative result is confirmed by visual comparison of real and virtual video, where the virtual video output is much more consistent and robust, with fewer occasions of tracking loss or unexpected movement compared with previous methods.

关键词： localization and tracking technologies Electromagnetic tracking 2D/3D image registration Endoscopic procedures Intraoperative imaging

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Calibration and Evaluation of a Magnetically Tracked ICE Probe for Guidance of Left Atrial Ablation Therapy

Calibration and Evaluation of a Magnetically Tracked ICE Pro...

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Conference on Medical Imaging - Image-Guided Procedures, Robotic Interventions and Modeling

作者： Linte, Cristian A. Rettmann, Maryam E. Dilger, Ben Gunawane, Mia S. Arunachalam, Shivaram Poigai Holmes, David R., III Packer, Douglas L. Robb, Richard A. Mayo Clin Biomed Imaging Resource Rochester MN 55902 USA Mayo Clin Dept Physiol & Biomed Engn Rochester MN 55902 USA Mayo Clin Div Cardiol Rochester MN 55902 USA Univ Iowa Carver Coll Med Iowa City IA 52242 USA Georgetown Univ Med Ctr Dept Biochem & Mol & Cellular Biol Washington DC 20007 USA

ISBN: (纸本)9780819489654

The novel prototype system for advanced visualization for image-guided left atrial ablation therapy developed in our laboratory permits ready integration of multiple imaging modalities, surgical instrument tracking, interventional devices and electro-physiologic data. This technology allows subject-specific procedure planning and guidance using 3D dynamic, patient-specific models of the patient's heart, augmented with real-time intracardiac echocardiography (ICE). In order for the 2D ICE images to provide intuitive visualization for accurate catheter to surgical target navigation, the transducer must be tracked, so that the acquired images can be appropriately presented with respect to the patient-specific anatomy. Here we present the implementation of a previously developed ultrasound calibration technique for a magnetically tracked ICE transducer, along with a series of evaluation methods to ensure accurate imaging and faithful representation of the imaged structures. Using an engineering-designed phantom, target localization accuracy is assessed by comparing known target locations with their transformed locations inferred from the tracked US images. In addition, the 3D volume reconstruction accuracy is also estimated by comparing a truth volume to that reconstructed from sequential 2D US images. Clinically emulating validation studies are conducted using a patient-specific left atrial phantom. Target localization error of clinically-relevant surgical targets represented by nylon fiducials implanted within the endocardial wall of the phantom was assessed. Our studies have demonstrated 2.4 +/- 0.8 mm target localization error in the engineering-designed evaluation phantoms, 94.8 +/- 4.6 % volume reconstruction accuracy, and 3.1 +/- 1.2 mm target localization error in the left atrial-mimicking phantom. These results are consistent with those disseminated in the literature and also with the accuracy constraints imposed by the employed technology and the clinical appl

关键词： Image-Guided Cardiac Procedures Intra-operative Imaging Ultrasound Guidance localization and tracking technologies Calibration

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Real-time motion compensation for EM bronchoscope tracking with smooth output - ex-vivo validation

Real-time motion compensation for EM bronchoscope tracking w...

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Conference on Medical Imaging - Image-Guided Procedures, Robotic Interventions and Modeling

作者： Reichl, Tobias Gergel, Ingmar Menzel, Manuela Hautmann, Hubert Wegner, Ingmar Meinzer, Hans-Peter Navab, Nassir Tech Univ Munich CAMP D-8000 Munich Germany German Canc Res Ctr Div Med BIo Informat Heidelberg Germany cKlinikum rechts Isar Munich Germany

ISBN: (纸本)9780819489654

Navigated bronchoscopy provides benefits for endoscopists and patients, but accurate tracking information is needed. We present a novel real-time approach for bronchoscope tracking combining electromagnetic (EM) tracking, airway segmentation, and a continuous model of output. We augment a previously published approach by including segmentation information in the tracking optimization instead of image similarity. Thus, the new approach is feasible in real-time. Since the true bronchoscope trajectory is continuous, the output is modeled using splines and the control points are optimized with respect to displacement from EM tracking measurements and spatial relation to segmented airways. Accuracy of the proposed method and its components is evaluated on a ventilated porcine ex-vivo lung with respect to ground truth data acquired from a human expert. We demonstrate the robustness of the output of the proposed method against added artificial noise in the input data. Smoothness in terms of inter-frame distance is shown to remain below 2 mm, even when up to 5 mm of Gaussian noise are added to the input. The approach is shown to be easily extensible to include other measures like image similarity.

关键词： localization and tracking technologies Endoscopic Procedures Intraoperative Imaging

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Absolute vs. Relative Error Characterization of Electromagnetic tracking Accuracy

Absolute vs. Relative Error Characterization of Electromagne...

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Conference on Medical Imaging 2010 - Visualization, Image-Guided Procedures, and Modeling

作者： Matinfar, Mohammad Narayanasamy, Ganesh Guitierrez, Luis Chan, Raymond Jain, Ameet Philips Res N Amer Dept Intervent Guidance Technol Briarcliff Manor NY USA

ISBN: (纸本)9780819480262

Electromagnetic (EM) tracking systems are often used for real time navigation of medical tools in an Image Guided Therapy (IGT) system. They are specifically advantageous when the medical device requires tracking within the body of a patient where line of sight constraints prevent the use of conventional optical tracking. EM tracking systems are however very sensitive to electromagnetic field distortions. These distortions, arising from changes in the electromagnetic environment due to the presence of conductive ferromagnetic surgical tools or other medical equipment, limit the accuracy of EM tracking, in some cases potentially rendering tracking data unusable. We present a mapping method for the operating region over which EM tracking sensors are used, allowing for characterization of measurement errors, in turn providing physicians with visual feedback about measurement confidence or reliability of localization estimates. In this instance, we employ a calibration phantom to assess distortion within the operating field of the EM tracker and to display in real time the distribution of measurement errors, as well as the location and extent of the field associated with minimal spatial distortion. The accuracy is assessed relative to successive measurements. Error is computed for a reference point and consecutive measurement errors are displayed relative to the reference in order to characterize the accuracy in near-real-time. In an initial set-up phase, the phantom geometry is calibrated by registering the data from a multitude of EM sensors in a non-ferromagnetic ("clean") EM environment. The registration results in the locations of sensors with respect to each other and defines the geometry of the sensors in the phantom. In a measurement phase, the position and orientation data from all sensors are compared with the known geometry of the sensor spacing, and localization errors (displacement and orientation) are computed. Based on error thresholds provided by the ope

关键词： Interventional guidance electromagnetic tracking calibration performance characterization localization and tracking technologies

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Estimating heart shift and morphological changes during minimally invasive cardiac interventions

Estimating heart shift and morphological changes during mini...

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Conference on Medical Imaging 2010 - Visualization, Image-Guided Procedures, and Modeling

作者： Linte, Cristian A. Carias, Mathew Cho, Daniel S. Pace, Danielle F. Moore, John Wedlake, Chris Bainbridge, Daniel Kiaii, Bob Peters, Terry M. Robarts Res Inst Imaging Res Labs London ON Canada Univ Western Ontario Biomed Engn Grad Program London ON Canada Univ Western Ontario Dept Med Biophys London ON Canada Univ Western Ontario Div Anesthesia London ON Canada Univ Western Ontario Div Cardiac Surg London ON Canada CSTAR London ON Canada

ISBN: (纸本)9780819480262

Image-guided interventions rely on the common assumption that pre-operative information can depict intraoperative morphology with sufficient accuracy. Nevertheless, in the context of minimally invasive cardiac therapy delivery, this assumption loses ground;the heart is a soft-tissue organ prone to changes induced during access to the heart and especially intracardiac targets. In addition to its clinical value for cardiac interventional guidance and assistance with the image-and model-to-patient registration, here we show how ultrasound imaging may be used to estimate changes in the heart position and morphology of structures of interest at different stages in the procedure. Using a magnetically tracked 2D transesophageal echocardiography transducer, we acquired in vivo images of the heart at different stages during the procedural workflow of common minimally invasive cardiac procedures, including robot-assisted coronary artery bypass grafting, mitral valve replacement/repair, or model-enhanced US-guided intracardiac interventions, all in the coordinate system of the tracking system. Anatomical features of interest (mitral and aortic valves) used to register the pre-operative anatomical models to the intraoperative coordinate frame were identified from each dataset. This information allowed us to identify the global position of the heart and also characterize the valvular structures at various peri-operative stages, in terms of their orientation, size, and geometry. Based on these results, we can estimate the differences between the pre- and intra-operative anatomical features, their effect on the model-to-subject registration, and also identify the need to update or optimize any pre-operative surgical plan to better suit the intra-operative procedure workflow.

关键词： Minimally Invasive Cardiac Procedures Data Integration for the Clinic/OR Pre-operative Procedure Planning Peri-operative Workflow Intra-operative Guidance localization and tracking technologies

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Enhancement of subsurface brain shift model accuracy: a preliminary study

Enhancement of subsurface brain shift model accuracy: a prel...

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Conference on Medical Imaging 2010 - Visualization, Image-Guided Procedures, and Modeling

作者： Garg, Ishita Ding, Siyi Coffey, Aaron M. Dumpuri, Prashanth Thompson, Reid C. Dawant, Benoit M. Miga, Michael I. Vanderbilt Univ Dept Biomed Engn Nashville TN 37235 USA Vanderbilt Univ Dept Elect Engn Nashville TN 37235 USA Vanderbilt Univ Med Ctr Dept Neurol Surg Nashville TN USA Vanderbilt Univ Med Ctr Dept Radiol & Radiol Sci Nashville TN 37232 USA

ISBN: (纸本)9780819480262

Biomechanical models that describe soft-tissue deformations provide a relatively inexpensive way to correct registration errors in image guided neurosurgical systems caused by non-rigid brain shifts. Quantifying the factors that cause this deformation to sufficient precision is a challenging task. To circumvent this difficulty, atlas-based method have been developed recently which allow for uncertainty yet still capture the first order effects associated with brain deformations. More specifically, the technique involves building an atlas of solutions to account for the statistical uncertainty in factors that control the direction and magnitude of brain shift. The inverse solution is driven by a sparse intraoperative surface measurement. Since this subset of data only provides surface information, it could bias the reconstruction and affect the subsurface accuracy of the model prediction. Studies in intraoperative MR have shown that the deformation in the midline, tentorium, and contralateral hemisphere is relatively small. The falx cerebri and tentorium cerebelli, two of the important dural septa, act as rigid membranes supporting the brain parenchyma and compartmentalizing the brain. Accounting for these structures in models may be an important key to improving subsurface shift accuracy. The goals of this paper are to describe a novel method developed to segment the tentorium cerebelli, develop the procedure for modeling the dural septa and study the effect of those membranes on subsurface brain shift.

关键词： localization and tracking technologies image-guided therapy modeling neurosurgical procedure brain shift finite element modeling dural septa tentorium cerebelli falx cerebri

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Effects of sensor orientation on AC electromagnetic tracking system accuracy in a CT scanner environment - art. no. 691823

Effects of sensor orientation on AC electromagnetic tracking...

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Medical Imaging 2008 Conference

作者： Shen, Eric Shechter, Guy Kruecker, Jochen Stanton, Douglas Philips Res N Amer Briarcliff Manor NY 10510 USA

ISBN: (纸本)9780819471024

The purpose of this study was to examine the effects of different sensor orientation on the positional accuracy of an AC electromagnetic tracking system, the second generation NDI Aurora, within a CT scanner enviromnent. A three-axis positioning robot was used to move three electromagnetically tracked needles above the CT table throughout a 30cm by 30cm by 30cm volume sampled in 2.5cm steps. All three needle tips were held within 2mm of each other, with the needle axes orthogonally located in the +x, +y, and +z directions of the Aurora coordinate system. The corresponding position data was captured from the Aurora for each needle and was registered to the positioning system data using a rigid body transformation minimizing the least squares L2-norm. For all three needle orientations the largest errors were observed farthest from the field generator and closest to the CT table. However, the 3D distortion error patterns were different for each needle, demonstrating that the sensor orientation has an effect on the positional measurement of the sensor. This suggests that the effectiveness of using arrays of reference sensors to model and correct for metal distortions may depend strongly on the orientation of the reference sensors in relation to the orientation of the tracked device. In an ideal situation, the reference sensors should be oriented in the same direction as the tracked needle.

关键词： localization and tracking technologies image-guided therapy modeling registration

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Object identification accuracy under ultrasound enhanced virtual reality for minimally invasive cardiac surgery

Object identification accuracy under ultrasound enhanced vir...

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Medical Imaging 2008 Conference

作者： Wiles, Andrew D. Moore, John Linte, Cristian A. Wedlake, Christopher Ahmad, Anis Peters, Terry M. Robarts Res Inst Imaging Res Labs London ON N6A 5C1 Canada

ISBN: (纸本)9780819471024

A 2D ultrasound enhanced virtual reality surgical guidance system has been under development for some time in our lab. The new surgical guidance platform has been shown to be effective in both the laboratory and clinical settings, however, the accuracy of the tracked 2D ultrasound has not been investigated in detail in terms of the applications for which we intend to use it (i.e., mitral valve replacement and atrial septal defect closure). This work focuses on the development of an accuracy assessment protocol specific to the assessment of the calibration methods used to determine the rigid transformation between the ultrasound image and the tracked sensor. Specifically, we test a Z-bar phantom calibration method and a phantomless calibration method and compared the accuracy of tracking ultrasound images from neuro, transesophageal, intracardiac and laparoscopic ultrasound transducers. This work provides a fundamental quantitative description of the image-guided accuracy that can be obtained with this new surgical guidance system.

关键词： calibration cardiac procedures localization and tracking technologies enhanced reality image-guided therapy intraoperative imaging ultrasound guidance validation

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